In many situations it would be desirable to have an inexpensive device to communicate by voice underwater. Divers, snorkelers and swimmers, for example, could use such a device. Also, such a device could be used as a toy.
A large difficulty in designing devices for talking underwater is in transferring the air sound waves of the voice to water sound waves while avoiding the formation of loud, disruptive air bubbles. Air exhaled while talking can form loud bubbles if allowed to freely escape into the surrounding water. Bubbles can often be loud enough to mask the voice of the speaker. The bubble noise problem is addressed in several prior art devices.
U.S Pat. No. 4,183,422 to Williams discloses a nonelectronic device for speaking underwater which uses an elastic bag which fits over the mouth. The bag surface functions as a diaphragm and so allows the transmission of sound waves. The bag also functions to prevent any air from escaping, which completely prevents the formation of disruptive air bubbles. This invention requires that the bag be at least partially inflated before speaking. A problem with this invention is that the bag is fragile and can be easily damaged.
U.S. Pat. No. 5,493,079 to Anderson discloses a nonelectronic device for speaking underwater which uses a tuned diaphragm attached to a snorkel tube. The tuned diaphragm couples sound waves to the water and the snorkel tube allows the speakers exhaled air to escape to the water surface without forming air bubbles. This solution requires that the speaker be very close to the water surface because loud bubbles will be created if the snorkel is submerged. Another difficulty with this invention is the fact that it requires the diaphragm to be tuned to the frequency range of 1500-3000 hertz. This can require more than one diaphragm. This invention also requires the inclusion of flexible lips for articulating plosive sounds. This is necessary because the invention is attached to a snorkel tube which is held in the mouth by the teeth.
U.S. Pat. No. 4,527,657 to Payne discloses a nonelectric device for speaking underwater which uses a special impedance matched tapered tube for transferring the sound waves to the water. Exhaled air is passed through a bubbles silencer which is worn around the users neck. The silencer consists of two rubber sheets bonded together around the edges. The rear portion of the silencer has an opening between the rubber sheets which allows the air to escape without making a lot of noise. However, the bubbles released are not substantially reduced in size by the bubbles silencer. This invention is rather sophisticated and expensive and, as such, is not intended for casual use by swimmers and snorkelers.